Border ruffians were proslavery raiders who crossed into the Kansas Territory from Missouri during the mid-19th century to help ensure the territory entered the United States as a slave state. Their activities formed a major part of a series of violent civil confrontations known as "Bleeding Kansas", which peaked from 1854 to 1858. Crimes committed by border ruffians included electoral fraud, intimidation, assault, property damage and murder; many border ruffians took pride in their reputation as criminals. After the outbreak of the American Civil War in 1861, many border ruffians fought on the side of the Confederate States of America as irregular bushwhackers.